For circulation/return, I'm using a pan world 200ps (1750gph). I'm hoping this will be enough. I'm making a large wet/dry and will have a 1000 gallon rated fluidized bed filter. At a later date I may add ozone, but I'm not sure. I may just stick with UV. I also have an aqua c ev-2000 skimmer. That turns out to be the most expensive part. It's rated at 2000 gallons. Right now I'm getting ready to place the returns and overflow in the sides of the pond. Then comes the liner. I'm not looking forward to the liner since it's difficult to get to all of the sides of the pond as it almost touches three walls of the room, and weighs 85 pounds. Hopefully I'll have some more progress pictures later this week.